1. Field of The Invention
The present invention relates generally to agricultural balers and, in particular, to density control methods and apparatus for such balers.
II. Prior Art and Other Considerations
Agricultural balers have a bale case into which crop or silage material is introduced. The bale case, generally of a rectangular shape, is defined by rails which determine the height and width of the bale case. A plunger is reciprocably disposed in a forward portion of the bale case to form crop material into rectangular bales These rectangular bales are pushed through a rearward portion of the bale case where they are bound in a conventional manner with suitable material such as twine before being discharged from the baler
In the baler art it is known that bale density may be controlled by changing the position of one or more of the rails defining the bale case. Numerous types of mechanisms have been provided for performing this function such as those shown in U.S. Pat. Nos. 4,125,071; 4,037,528; and 4,489,648. In various ones of these known mechanisms tensioning systems comprising hydraulic cylinders are actuated to change the position of the bale case rails.
Various prior art methods exist for controlling the actuation of the hydraulic cylinders and for thereby changing the position of the bale case rails in order to control the density of the material being baled therein. According to some prior art practices mechanical sensors attempt to penetrate a forming bale and determine whether the hydraulic cylinders are to be either further pressurized or depressurized. According to another prior art practice disclosed in U.S. Pat. Nos. 4,168,659 and 4,280,403, an attempt is made to keep the plunger operating at a constant compactive force regardless of variations in crop conditions by mechanically linking the plunger with a hydraulic pump. The linkage is effected in a manner whereby, with each compaction stroke of the piston, the pump routes additional pressure to a hydraulic circuit and to the hydraulic cylinders until a sufficient pressure level is reached in the hydraulic circuit. Careful and critical calibrations are required with respect to the hydraulic circuit in order to accommodate such prior art devices for the handling of different types of baled materials or the baling of materials under changing conditions
In view of the foregoing, it is an object of the present invention to provide a method and apparatus for accurately and effectively controlling the density of baled material.
An advantage of the present invention is the provision of method and apparatus wherein the density of baled material is controlled by directly sensing the stress on mechanical elements employed in compacting the bale.
A further advantage of the present invention is the provision of method and apparatus for controlling the density of baled material without tedious calibration.